1. Field of the Invention
The present invention pertains to antifouling additives for paints containing matrices cross-linked with lanthanide elements or lanthanide element derivatives and their use. More particularly the present invention pertains to antifouling paints containing a wood matrix or wood-derived matrix and one or more members of the group consisting of lanthanide elements and lanthanide element derivatives.
2. Discussion of the Prior Art
Antifoulants are an important class of additives for paints that are primarily used on surfaces exposed to a marine environment. Marine organisms, such as barnacles, seaweed algae, bacteria, fungi and protozoa, tend to colonize those surfaces rapidly and to a great extent. When such colonization occurs on hulls of marine vessels, for instance, the effect on increased fuel cost is considerable. It is estimated that the increased fuel cost may be as much as 30% above fuel costs under normal conditions. Controlling or preventing the growth of marine organisms is therefore an important concern for mariners as well as marine paint manufactures.
Copper oxide is one of the most widely used antifouling agents. It is added in unusually large amounts and may constitute from 40 to 70% of the coating weight. In order to increase the fouling free life of the coating, the thickness of it is commonly doubled or tripled. Copper oxide is used in insoluble as well as soluble coating matrices. The mechanism of action is due to leaching triggered by interaction with the marine organisms upon contact, or a slow release mechanism associated with binding loss, e.g., reduced binding with rosin. The protection can last up to about a year. The leaching of the toxicant copper oxide in the environment has been a health concern.
Other antifoulants used alone or in combination with copper oxide are organo-tin compounds such as tributyl tin oxide, tributyl tin floride, triphenyl tin floride as well as organo-tin polymers such as acrylate. They also act on the principle of toxicant release. While the diffusional transport of copper oxide is exponential over time, the toxicant release from the acrylate-tin polymer has the advantage of being linear. Release from the TBTO and TBTF in salt water is in the order of 10-25 ppm. The organ-tins are more toxic than the copper oxide and are also difficult to form. They are used in amounts between 0.5 and 12% in coating formulations.
The ideal antifoulant should have a broad spectrum of activity, long duration and low toxicity. It is an objective of this invention to provide a new, safe and effective antifouling additive for marine coatings by using lanthanide elements or lanthanide element derivatives. These and other objects are met by the present invention and are further described in the specifications.
Lanthanide derivatives are used in glass, ceramic, paint, platics, and rubber manufacture. Compositions comprising cerium compounds are known to have bacteriocidal effects, e.g., compositions comprising cerium nitrate and silver sulfadiazine (Boechx, et al., Burns vol. 11, no. 5 (1985) pp. 337-342; Monafo, 3rd International Congress on Pharmacological Treatment of Burns, Milan, Italy, May 12-15 1980, Panmainerva Med., vol. 25, no. 3 (1983) pp. 151-154, Bowser, et al., J. Trauma, vol. 21, no. 7 (1981) pp. 558-563; Monafo, et al., Arch. Surg, vol. 113, no. 4 (1981) pp. 397-401; Monafo, et al., Surgery (St. Louis) vol. 80, no. 4 (1976) pp. 465-473), and compositions containing electrically activated silver and cerium stearate (Colmano, et al., 23rd Annual Meeting of the Biophysical Society (New York), Atlanta Ga., Feb. 26-28, 1979, Biophys. J. vol. 25, no. 2, part 2 (1979) p. 217A). Cerium derivatives are also used as additives in plastics for food packaging.
The above mentioned use of lanthanides in paint pertain more particularly to cerium octoate and naphthenate that are used in small quantities to facilitate drying. These water insoluble cerium derivatives act as polymerization catalysts.